1. Field of the Invention
The present invention relates to liquid injection and atomization, and more particularly to multi-point fuel injection such as in gas turbine engines.
2. Description of Related Art
A variety of devices are known for injecting or spraying liquids, and for atomizing liquids into sprays of fine droplets, such as for gas turbine engines. Improvements in spray patternation have been made by recent developments in multi-point injection, in which a single injector will include multiple individual injection orifices. Exemplary advances in multi-point injection are described in commonly assigned U.S. Patent Application Publications No. 2011/0031333 and 2012/0292408. These designs employ swirl features formed or machined in injector components to generate swirl in flows of liquid and/or air issuing from each injection point.
In a more general aspect, it is desirable in many applications for the spray angle of a nozzle or injector to change during operation. For example, during start up of a gas turbine engine, it is desirable for fuel nozzles to have a wide spray angle in order to position fuel flow in proximity with igniters, which are typically on the periphery of the surrounding combustor. After combustion has been initiated, it may be desirable to have a narrower spray angle to achieve deeper spray penetration into the combustor. These two different spray angles can be accomplished using nozzles with two stages, each having a different spray angle. The extra components required to produce the two stages require envelope space and add to part count. It may also be possible to change the spray angle by physically changing the nozzle geometry. This approach has not become main stream, due to the complications of actuating components to change the nozzle geometry within the combustion environment.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for multi-point injection that provides swirling flows with simplified geometry and manufacturing. There also remains a need in the art for simplified nozzles and injectors that can change spray angle during operation. The present invention provides a solution for these problems.